<ActiveItem()>
Public Class TimerTest
     Private Property OutputProperty As IItemProperty ' the ItemProperty object for CustomItem.Output
     Private Property TimedCallbackService As ITimedCallbackService ' timer service
     Private Property TimerKey As Object ' will be != Nothing while timer is running

     ' Inputs

     <Input(IsCommand:=True)>
     Public Property Trigger As Boolean

     ' Outputs

     <Output()>
     Public Property Out As Boolean

     Public Sub Execute(ByVal context As ICustomItemCallContext)
         If context.ChangedInputName = "Trigger" Then
             If OutputProperty Is Nothing Then
                 ' Initialize OutputProperty if not yet done
                 Dim propertyDescriptor As IItemPropertyDescriptor = context.Project.GetItemClassByName("CustomItem").GetPropertyByName("Output")
                 OutputProperty = context.Item.GetProperty(propertyDescriptor)
             End If
             If TimedCallbackService Is Nothing Then
                 ' Initialize TimedCallbackService if not yet done
                 TimedCallbackService = DirectCast(context.Project, IServiceProvider).GetService(GetType(ITimedCallbackService))
             End If
             If TimerKey Is Nothing Then
                 ' Timer not already running
                 ' start timer; will elapse in 1 second
                 TimerKey = TimedCallbackService.Register(AddressOf DelayTimeElapsed, DateTime.UtcNow + TimeSpan.FromSeconds(1), Nothing)
             End If
         End If
     End Sub
     ' This method will be called one second after we got a pulse on the Trigger input
     Private Sub DelayTimeElapsed(ByVal timerKey As Object, ByVal data As Object)
     TimerKey = Nothing
         Out = Not Out ' flip Out
         ' Write directly to Server property, since the custom item element will
         ' pick up the Out property value only after calling Execute
         OutputProperty.Value = New Object(0) {Out}
     End Sub
End Class